Seed grains are sold in sacks whose contents are determined not by the mass of the sack, but by the number of grains in the sack. For a sack of corn grain, this number is around 80,000.
The problem in bagging seed grains comes from the fact that seed grains naturally have different granulometric characteristics. Consequently, it is not possible to define the contents of a sack of seed grain by a mass of grains that would correspond to the predetermined number of grains required to fill a sack.
Traditionally, grain bagging is done in the following phases: the grain is first calibrated and then it is stored in different silos by caliber. For each caliber of grain, the mass of the number of grains required to fill a sack is known. (A sack of 80,000 high-caliber grains will be heavier than a sack of 80,000 low-caliber grains). The calibrated grains are then bagged by a bagging machine; the bagging operation is controlled by a scale whose index value is set on the basis of the caliber of the grains in the lot to be bagged. For each lot of grain to be bagged of different caliber, a different index value is set on the scale.
This seed grain bagging process usually used has many disadvantages, namely:
the calibrating operation is difficult to carry out with precision, PA1 during calibration, a proportion of grain that may reach 10% is lost, PA1 calibration is a stressful operation for the grain, PA1 calibration is an expensive operation in terms of resources and time, PA1 it is necessary to store and manage stocks of grain of different calibers, PA1 the error in the number of grains per sack may reach 5% more or less. PA1 grains are collected from a flow of grain intended to be put into sacks, PA1 the grains collected are subjected to a vibration operation to ensure distribution of the grain and to take them to an acceleration device, PA1 the grains go onto an inclined acceleration chute in order to single them out, PA1 the grains are counted by counting cells located at the bottom of the acceleration channels, PA1 when the grains are counted, the feeding of the channels of the acceleration chute is stopped, PA1 the counted grains are weighed, PA1 the number n of grains and the mass of that number n of grains are sent to a calculator that takes these data and finds the theoretical mass of the predetermined number of grains in a sack, PA1 the flow of grains fills a sack placed on a weighing system whose index value is the theoretical mass found by the calculator, PA1 when the theoretical mass is measured by the weighing system, the weighing system orders the sack filling to stop, PA1 the phases described above are repeated at predetermined intervals until the flow of grain to be bagged is exhausted, PA1 the index value of the weighing system is updated each time the calculator finds the theoretical mass of the predetermined number of grains in a sack. PA1 a nozzle for collecting grain arranged on the means of conveying the grain, PA1 a horizontal vibrating plate, equipped with channels on the side receiving the grain, with vibrations that ensure distribution of the grains in each of the channels and a shifting movement of the grain, PA1 a chute that includes channels into which the grain slides; the chute is inclined at an angle so that the grain in it is subject to an almost free fall, PA1 means of counting located perpendicular to each channel of the chute, PA1 a weighing hopper to take the grain after counting, PA1 means of controlling the vibrations of the horizontal plate, PA1 means of weighing the grain counted, PA1 a calculator that takes in data related to the number of grains and data related to the mass of that number of grains; these data make it possible to find the theoretical mass of the predetermined number of grains in a sack, PA1 means of weighing the sack, known by themselves, whose index value is the theoretical mass found by the calculator, when that theoretical mass is measured by the weighing system, the weighing system orders the sack filling to stop.
A bagging device is also known from document DE 38 02 268. This device consists of taking grain samples from a flow of grain intended to be bagged. From these samples, the unit mass of the grain is calculated.
Knowing the number of grains that are to be bagged, the total mass of the number of grains that should comprise one sack is deduced from the unit mass of the grains composing the sample.
The operation counting the number of grains in the sample is not specified in this document. But that operation is essential, since the precision of the index value assigned to the bagging scale depends directly on the precision with which the grain counting is done.